Numerous devices have been proposed in the past for detachably mounting a snow plow to the front of a vehicle, such as a truck. For the most part these require some vehicle attachment structure either to the bumper or have frame members such as a lift tower and light bar assembly which project in front of the bumper or, have a lift tower mechanism projecting upwardly between the bumper and the front grill of the vehicle. In most of these arrangements, the attachment structure remains on the vehicle during normal use (e.g., during non-plowing operations when the plow and its support frame are stored), and they, in effect, disable or in part disable the shock absorbing properties of the bumper and the operation of the bumper in actuating air bag deployment and the like. In addition, these attachment structures are generally unsightly and sometimes dangerous. In most cases, the prior art systems require fairly precise alignment (both vertically and horizontally) of parts on the plow itself and vehicle mounted parts during the attachment procedure. Very often, it requires two persons, one to drive the vehicle and, the other to either lift and make the alignment as the vehicle approaches to align the plow and the vehicle.
In addition, some recent mounting arrangements which seek to solve the bumper problems require a three-point connection to the vehicle, typically two spaced at a lower level below the bumper and one (or more) spaced above the bumper for connecting a lift mechanism to the plow frame to allow the frame to be lifted for transportation purposes. Moreover, such systems do not allow for slight horizontal and vertical misalignments between the attachment components permanently mounted on the vehicle and complementary attachment components on the plow support frame.
The present invention solves the above problems by providing a two-point coupling and suspension system in which a vehicle mounted attachment frame is secured to the frame of the vehicle and has a pair of spaced sockets which are positioned below and slightly behind the forward-most end surface of vehicle bumper when the vehicle mount attachment frame is mounted on the vehicle. The sockets include a first pair of reaction bearing surfaces aligned with and to the rear of the spaced sockets and a transverse latch bar forward of the reaction bearing surfaces. An intermediate support frame has a pair of rearwardly extending latching arms which extend in a rearward direction and have further reaction bearing surfaces for bearing against the respective ones of the first pair of reaction bearing surfaces when the plow has been lifted. The sockets have diverging plates which guide the rearwardly extending latching arms and thus horizontally aligns the arms with their respective sockets. Camming surfaces on the rearwardly extending latching arms engage a transverse latch bar and correct for vertical misalignments.
A support frame for supporting snow plow blade means has a rearward end pivotally connected to the intermediate frame for rotation about a horizontal axis. A lift mechanism is coupled between the intermediate support frame and the support frame for pivoting the support frame about the horizontal axis and for lifting the support frame and working implement off the ground such that the weight thereof is borne by the reaction bearing surfaces and the said pair of spaced socket means. One or more latch dogs are rotated by an over-center toggle linkage to lock the latch arms in their respective sockets.
In one preferred embodiment, the lift mechanism incorporates a pair of laterally spaced hydraulic lift cylinders. In a further preferred embodiment, the hydraulic lift cylinders are single acting and, in another embodiment, the lift cylinders are double-acting. In the case of single acting lift cylinders (or double acting cylinders operated as a single acting cylinder), hydraulic fluid is admitted to one side of the piston to force the piston towards the opposite end. Springs or the weight of the load system return the piston to the opposite end when the hydraulic pressure is released. In a further preferred embodiment, the hydraulic pressure is applied to both sides of the hydraulic piston head to positively drive it in both directions. This latter embodiment is very useful when it is desired to pack the snow or otherwise handle the snow more efficiently. The double-acting lift cylinder arrangement provides a capability to obtain pressure on the plow when using the appropriate control valve and is desirable for cutting matte or ice build-up and for stacking the snow.
In a further embodiment, instead of a pair of side-mounted hydraulic cylinders, a single acting hydraulic lift cylinder is centrally positioned on the coupler assembly upright members and a projecting arm is actuated in a vertical plane. A chain, coupled to the center of the projecting arm and to the plow support frame operates in a conventional fashion to pivot the frame about the horizontal pivot.
While in the preferred embodiment the plow blade support frame is a "T"-frame as disclosed in the above-referenced Quenzi patent, and the blade is constituted by a pair of centrally hinged plow blades, it will be appreciated that the plow blades may be constituted by a single blade. Moreover, while the blades are positioned using hydraulic cylinders, equivalent electrical or manual blade positioning or angle adjusting mechanism may be employed. In addition, while the "T"-frame of the above-reference Quenzi patent is preferred, an "A"-frame or other frame system may be used as the plow blade support and load transmitting frame.
A further feature of the invention is the provision of a friction mechanism so that the angle between the intermediate support frame and the support frame is maintained when the plow is rested on the ground for disengagement from the truck. In accordance with this feature, a support strap or slide bar is pivotally mounted on one of the plow support frame or intermediate frame and is provided with an elongated slot. The slotted portion of the slide bar is clamped between two pieces of plastic material (UHMW polyethylene or equivalent) with sufficient force to hold the weight of the components when the snow plow is off the truck but not so tight as to prevent lifting of the plow with one or more lift cylinders. This holds the coupler and the power unit and light bar assembly in position relative to the frame when the plow is off the truck and thus provides for easy one- person attachment of the plow to the truck since the projecting ends of the intermediate coupling unit are generally aligned with the truck when the plow blades have been lowered to the ground for storage or disengagement purposes.